| 1. |
- Bratt, Tomas, et al.
(författare)
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Cleavage of the alpha 1-microglobulin-bikunin precursor is localized to the Golgi apparatus of rat liver cells
- 1993
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Ingår i: Biochimica et Biophysica Acta. - 0006-3002. ; 1157:2, s. 54-147
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Tidskriftsartikel (refereegranskat)abstract
- alpha 1-Microglobulin, a plasma protein with immunoregulatory properties, and bikunin, the light chain of the proteinase inhibitors inter-alpha-inhibitor and pre-alpha-inhibitor, are translated as a precursor protein from the same mRNA. The cosynthesis of alpha 1-microglobulin and bikunin is unique compared to other proproteins such as procomplement components and prohormones, since alpha 1-microglobulin and bikunin have no known functional connection. Different forms of intracellular rat liver alpha 1-microglobulin were isolated and characterized by amino acid sequence analysis, lectin binding and glycosidase treatment. Their subcellular distribution was studied by Nycodenz and sucrose gradient centrifugation, pulse-chase experiments, and electrophoresis with subsequent immunoblotting, using pro-C3 and prohaptoglobin as reference proteins. Two alpha 1-microglobulin-bikunin precursors (40 and 42 kDa), containing one and two N-linked oligosaccharides, respectively, were detected in the endoplasmic reticulum. After transport to the Golgi apparatus, the precursors were cleaved, probably C-terminal to the sequence Arg-Ala-Arg-Arg immediately preceding the bikunin part, yielding free sialylated 28 kDa alpha 1-microglobulin, representing the mature protein. The cleavage was almost complete in phosphatidylinositol 4-kinase-enriched membranes, previously identified as a post-Golgi compartment. A fourth intracellular form of alpha 1-microglobulin, 26 kDa, lacked sialic acid. None of the intracellular forms carried the yellow-brown chromophore associated with alpha 1-microglobulin when purified from serum and urine, suggesting that this chromophore becomes linked to the protein after its secretion from the liver cells.
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| 2. |
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| 3. |
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| 4. |
- Gierow, Peter, et al.
(författare)
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Fractionation of rat liver plasma membrane regions by two-phase partitioning
- 1986
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Ingår i: Biochemical journal. ; 235, s. 685-691
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Tidskriftsartikel (refereegranskat)abstract
- Rat liver plasma membranes, enriched in blood-sinusoidal or bile-canalicular regions by differential andsucrose-gradient centrifugation, were further purified by partitioning in an aqueous polymer two-phasesystem. This method separates membranes according to differences in surface properties rather than size anddensity. A several-fold increase in the ratio of leucine aminopeptidase (a bile-canalicular marker) and5'-nucleotidase to asialo-orosomucoid binding (a blood-sinusoidal marker) was obtained in one fraction,whereas another fraction gave a 2-3-fold increase in ratio of blood-sinusoidal to bile-canalicular markers.Furthermore, the markers for both regions of the plasma membrane, as well as markers for Golgi membranesand lysosomes, showed a heterogeneous behaviour on counter-current distribution.
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| 5. |
- Gierow, Peter, et al.
(författare)
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Heterogeneity of smooth endoplasmic reticulum from rat liver studied by two-phase partitioning
- 1989
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 262:1, s. 55-61
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Tidskriftsartikel (refereegranskat)abstract
- Smooth microsomal membranes, prepared from rat liver by sucrose-density-gradient centrifugation, were subfractionated by counter-current distribution in an aqueous two-phase system consisting of poly(ethylene glycol) and Dextran T500. A comparison of the distribution curves of marker enzymes, together with theoretically calculated curves, indicated the presence of at least five membrane subfractions, differing in the ratios of the marker enzymes. Glucose-6-phosphatase and arylesterase distributed in one manner, and NADPH-cytochrome c reductase and NADH-ferricyanide reductase in another. Evidence for further heterogeneities in the distribution of marker enzymes in smooth microsomes was obtained by analysing the membrane domain structure using a recently described method [Albertsson (1988) Q. Rev. Biophys. 21, 61-98]. Phenobarbital treatment did not influence the behaviour of the marker enzymes.
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| 6. |
- Gierow, Peter, et al.
(författare)
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Lateral heterogeneity of rat liver plasma membranes analysed by counter-current distribution
- 1988
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Ingår i: Biochemical Journal. - 0264-6021 .- 1470-8728. ; 249, s. 369-375
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Tidskriftsartikel (refereegranskat)abstract
- The lateral heterogeneity of rat liver plasma membranes was examined by fragmentation and fractionation by counter-current distribution in an aqueous two-phase polymer system. The distribution pattern was analysed by plotting the relative specific activities of marker components against each other. By this analysis asialo-orosomucoid receptors were found in a domain separated from domains containing 5'-nucleotidase and leucine aminopeptidase by another domain devoid of these markers. 5'Nucleotidase and leucine aminopeptidase resided in adjacent but separate domains. The experimental data were compared with corresponding plots of markers in model membranes. The model membranes yielded plots of different shapes depending on marker distribution and fragment size. This method of analysis should be useful for examining the lateral heterogeneity also of other membranes.
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| 7. |
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| 8. |
- Gierow, Peter, et al.
(författare)
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Two-phase partitioning of rat liver plasma membranes
- 1989
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Ingår i: Plenum Press In: Fisher, D. & Sutherland, I. (eds) Separations using aqueous phase systems. Applications in cell biology and biotechnology. - New York.
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Konferensbidrag (refereegranskat)
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